What are the extra subdirectories returned by dir function?

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John
John 2018-11-19
评论： Guillaume 2019-4-4
When using the dir function, the first two elements returned have name field values of '.' and '..', which are determined to be directories by the dir function. However, these directories are not created nor do they appear in the directory window. Where do these directories come from?
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Guillaume
Guillaume 2019-4-4
the first two elements returned have name field values of '.' and '..'
They are not always the first two elements. Assuming that . and .. are always the first two elements returned by dir will lead to bugs. See my answer for more details.

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采纳的回答

Matt J
Matt J 2018-11-19
编辑：Matt J 2018-11-19
If you do
>> cd ..
and
>> cd .
you will see that they are aliases for the parent folder and the current folder, respectively.

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Guillaume
Guillaume 2018-11-19
编辑：Guillaume 2018-11-19
<rant mode on> They're absurd hold overs from a long gone era (DOS) where knowing that the current directory had a parent was somewhat useful. . always refers to the current directory, .. to the parent of the current directory. Nowadays, it's just clutter and I wish dir didn't return them as inevitably, you need to filter them out. Modern file handling code (e.g. .Net System.IO.Directory.GetDirectories) only return the list of actual folders.<end rant>
Note that the safe way to filter out these entries is with
filefolderlist = dir(somepath);
filterelist = filefolderlist(~ismember({filefolderlist.name}, {'.', '..'}));
Do not remove the first two entries as . and .. are not always first. Folders starting with a + for example will be listed before them.

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